Digitizer sensors are used for touch detection in many Human Interface Devices (HID) such as laptops, track-pads, MP3 players, computer monitors, and smart-phones. Capacitive sensors are one type of digitizer sensor. The capacitive sensor senses positioning and proximity of a conductive object such as a conductive stylus or finger used to interact with the HID. The capacitive sensor is often integrated with an electronic display to form a touch-screen. Capacitive sensors include antennas or lines constructed from different media, such as copper, Indium Tin Oxide (ITO) and printed ink. ITO is typically used to achieve transparency. Some capacitive sensors are grid based and operate to detect either mutual capacitance between electrodes at different junctions in the grid or to detect self-capacitance at lines of the grid. Finger touch interaction may be tracked based on a mutual capacitive or self-capacitive detection method. Mutual capacitive detection is typically used for tracking more than one finger touch interaction at a time.
Signal emitting styluses, e.g. active styluses, are known in the art for use with a digitizer sensor. Position of the stylus is tracked by picking on a signal emitted by the stylus with the digitizer sensor. Some active styluses emit a signal that includes information. A circuit associated with the digitizer sensor may decode and report the information to the HID. Some digitizer sensors are operated to track both finger touch input as well input from a signal emitting stylus.